Combustion devices that employ a metal piston and rigid combustion chamber to generate mechanical power are well developed and widely used.
Conventional combustion devices tend to be relatively heavy and non-portable. At smaller scales and lower weights, the efficiency of combustion systems rapidly decreases. Small-scale engines also suffer from leakage in the piston-cylinder gap, which is normally a negligible loss for larger engines. Since the piston-cylinder gap cannot be readily scaled down with engine size, leakage becomes more problematic as engine size decreases. Other problems associated with rigid combustion-based systems—at any size—include corrosion, temperature warping in small gaps, and wear. Rigid combustion systems of any size also need to be relatively heavy to achieve the rigidity needed to maintain tight tolerances in the piston-cylinder gap.
Many portable devices employ one or more batteries as a power source. Disposable or rechargeable batteries are used in most portable electronic devices for example. Intermittent bursts of power are important in the design and operation of many portable devices, where batteries often fall short. Batteries by themselves also offer no mechanical output; electrical output from them must be supplied to a motor to produce mechanical work.
In view of the foregoing, alternative power generation and combustion devices, particularly those suitable for mobile and portable use, would be desirable.